Endoscopic surgical instruments are often preferred over traditional open surgical devices since the use of a natural orifice tends to reduce the post-operative recovery time and complications. Consequently, significant development has gone into a range of endoscopic surgical instruments that are suitable for precise placement of a working end of a tool at a desired surgical site through a natural orifice. These tools can be used to engage and/or treat tissue in a number of ways to achieve a diagnostic or therapeutic effect.
Endoscopic surgery requires that the shaft of the device be flexible while still allowing the working end to be articulated to angularly orient the working end relative to the tissue, and in some cases to be actuated to fire or otherwise effect movement of the working end. Integration of the controls for articulating and actuating a working end of an endoscopic device tend to be complicated by the use of a flexible shaft and by the size constraints of an endoscopic instrument. Generally, the control motions are all transferred through the shaft as longitudinal translations, which can interfere with the flexibility of the shaft. There is also a desire to lower the force necessary to articulate and/or actuate the working end to a level that all or a great majority of surgeons can handle. One known solution to lower the force-to-fire is to use electrical motors. However, surgeons typically prefer to experience feedback from the working end to assure proper operation of the end effector. The user-feedback effects are not suitably realizable in present motor-driven devices.
Accordingly, there remains a need for improved methods and devices for controlling movement of a working end of an endoscopic surgical device.